1. Field of the Invention
The present invention relates to an optical reproducing apparatus and method, optical recording apparatus and method, and optical recording medium and particularly to an optical reproducing apparatus and method, optical recording apparatus and method which enables accurate recording and reproducing of data.
2. Description of the Related Art
FIG. 1 illustrates an application example of an optical disc drive. The optical disc drive 2 records the data supplied from a personal computer to a loaded optical disc 3 (for example, CD-R (Compact Disc-Recordable), CD-RW (Compact Disc-Rewritable) or CD-ROM (Compact Disc-Read Only Memory) or reproduces the data recorded on an optical disc 3 to output to a personal computer 1.
In the case where data recorded in an optical disc 3 is reproduced, an optical disc drive 2 radiates the laser beam in the laser power (hereinafter referred to as read power) for reproducing to the signal surface of the optical disc 3 rotating at the predetermined velocity and the light beam (reflected beam) which has been modulated depending on existence of signal (pit) from the signal surface is then converted to an electronic signal. In recent years, the optical disc 3 is caused to rotate at the higher rotating velocity. At present, the disc is rotated practically at the velocity which ranges from the standard velocity (210 rpm at the external circumference of optical disc) to the 24-fold velocity (5040 rpm at the external circumference of optical disc).
However, it is known that the higher the disc 3 rotates in the velocity, the more the C/N ratio is deteriorated at the time of reproducing operation. FIG. 2 illustrates a C1 error in the radius direction of the optical disc 3 which is driven with CAV (Constant Angular Velocity) system. When the optical disc 3 is driven with the CAV system, the rotating velocity of disk becomes higher in the area becoming nearer to the external circumference. Therefore, as a result, FIG. 2 illustrates relationship between the rotating velocity and C1 error.
In FIG. 2, the line A indicates the relationship between the rotating velocity and C1 error in the data reproducing operation when the laser beam of the lowest read power is radiated, while the line B when the laser beam of the read power B higher than the read power A is radiated and the line C when the laser beam of the read power C higher than the read power B is radiated. In any case, when the rotating velocity becomes higher, the C1 error becomes larger.
However, in the case of read power B (line B), the C1 error during high speed rotation is smaller than that in the read power A (line A) and in the case of read power C (line C), the C1 error during high speed rotation is smaller than that in the read power B (line B). Namely, when the read power is higher, the C1 error becomes smaller during the high speed rotation. Therefore, it is considered that the deterioration of C/N ration during high speed rotation can be prevented by using higher read power, but when the laser power having excessively higher read power is used, a problem is in turn generated during the recording operation.
For example, on the occasion of recording the data to an optical disc 3 in the optical disc drive 2, the laser beam in the intensity in which the laser power for recording (hereinafter write power) is further added to the read power radiates, as illustrated in FIG. 3, the signal surface of the optical disc 3 rotating at the predetermined rotating velocity. Thereby, pits are formed on the signal surface of optical disc 3 to record the data. However, if the read power is too high, total intensity of laser beam radiating the optical disc 3 becomes too high and the pits are thereby deformed. As a result, the data is no longer recorded accurately. Particularly, when the optical disc 3 is rotating at a lower velocity (for example, at the standard rotating velocity), deformation of pits is generated easily.
Therefore, intensity of read power is naturally limited and after all, it is a problem that data is reproduced by rotating the optical disc 3 at a higher rotating velocity at the time of recording operation without generation of any discrepancy.
The present invention has been proposed considering the situation explained above and it enables high speed rotation of the optical disc without generation of discrepancy during the recording operation.
According to one aspect of the present invention, an optical reproducing apparatus is characterized in comprising a detecting means for detecting the rotating velocity of a recording medium, a determining means for determining the optical read power corresponding to the rotating velocity detected by the detecting means and a radiating means for radiating the optical beam in the optical read power determined with the determining means to a recording medium.
According to another aspect of the present invention, an optical reproducing apparatus is characterized in comprising a determining means for determining, as a detecting means for detecting the rotating velocity of a recording medium, the rotating velocity based on the TOC information read from the recording medium and also determining the optimum read power corresponding to the rotating velocity detected with the detecting means and a radiating means for radiating the optical beam having the optimum read power determined with the determining means to the recording medium.
According to another aspect of the present invention, the optical reproducing apparatus further comprises a storage means for calculating and storing the amplification factor of a tracking error signal and offset value of the tracking error signal based on the amplitude of the tracking error signal when the focus control is performed and the tracking control is not performed under the condition that the optical beam of the optimum read power is radiated and a setting means for calculating, when the optical beam of the optimum read power is radiated to the recording medium, the amplification factor and offset value of the focus error signal in inverse proportion to amount of change of the read power and also setting such amplification factor and offset value to the radiating means with the amplification factor and offset value of the tracking error signal stored in the storage means, wherein the radiating means radiates, to the recording medium, the optical beam in the optimum read power determined with the determining means based on the amplification factor and offset value of the focus error signal and the amplification factor and offset value of the tracking error signal set by the setting means.
According to another aspect of the present invention, the optical reproducing method is characterized in comprising a detecting step for detecting rotating velocity of a recording medium, a determining step for determining the optimum read power corresponding to the rotating velocity detected in the detecting step and a radiating step for radiating the optical beam of the optimum read power determined with the determining step to the recording medium.
According to another aspect of the present invention, the optical reproducing method is characterized in comprising a determining step for determining, as the detecting step for detecting the rotating velocity of the recording medium, the rotating velocity based on the TOC information read from the recording medium and also determining the optical read power corresponding to the rotating velocity detected in the detecting step and a radiating step for radiating, to the recording medium, the optical beam of the optimum read power determined in the determining step.
According to another aspect of the present invention, the recording medium is characterized in comprising a detecting step for detecting the rotating velocity of the recording medium, a determining step for determining the optimum read power corresponding to the rotating velocity detected in the detecting step and a radiating step for radiating, to the recording medium, the optical beam of the optimum read power determined in the determining step.
According to another aspect of the present invention, the recording medium is characterized is comprising a determining step for determining, as the detecting step for detecting the rotating velocity of the recording medium, the rotating velocity based on the TOC information read from the recording medium and also determining the optimum read power corresponding to the rotating velocity detected in the detecting step and a radiating step for radiating the optical beam of the optimum read power determined in the determining step to the recording medium.
In the optical reproducing apparatus, optical reproducing method and recording medium of the present invention, the rotating velocity of a recording medium is detected, the optimum read power corresponding to detected rotating velocity is determined and the optical beam of the determined optical read power is radiated to the recording medium.
According to another aspect of the present invention, the optical recording apparatus is characterized in comprising a detecting means for detecting the rotating velocity of a recording medium, a determining means for determining the optimum read power corresponding to the rotating velocity detected with the detecting means and a radiating means for radiating, to the recording medium, the optical beam of the power in which the write power is added to the optimum read power determined in the determining means.
According to another aspect of the present invention, the optical recording apparatus is characterized in comprising a determining means for determining, as the detecting means for detecting the rotating velocity of the recording medium, the rotating velocity based on the TOC information read from the recording medium and also determining the optimum read power corresponding to the rotating velocity detected in the detecting means and a radiating means for radiating, to the recording medium, the optical beam of the power in which the write power is added to the optimum read power determined in the determining means.
According to another aspect of the present invention, the optical recording apparatus further comprises a storage means for calculating and storing the amplification factor of a tracking error signal and offset value of the tracking error signal based on the amplitude of the tracking error signal when the focus control is performed and the tracking control is not performed under the condition that the optical beam of the optimum read power is radiated and a setting means for calculating, when the optical beam of the optimum read power is radiated, the amplification factor and offset value of the focus error signal in inverse proportion to amount of change of the read power and also setting such amplification factor and offset value stored to the radiating means with the amplification factor and offset value of the tracking error signal stored in the storage means, wherein the radiating means radiates, to the recording medium, the optical beam of the optimum read power determined with the determining means based on the amplification factor and offset value of the focus error signal and the amplification factor and offset value of the tracking error signal set by the setting means.
According to another aspect of the present invention, the optimum read power in the optical recording apparatus is about 25% or less of the write power.
According to another aspect of the present invention, the optical recording method is characterized in including the detecting step for detecting the rotating velocity of a recording medium, a determining step for determining the optimum read power corresponding to the rotating velocity detected in the detecting step and the radiating step for radiating, to the recording medium, the optical beam in which the write power is added to the optimum read power determined in the determining step.
According to another aspect of the present invention, the optical recording method is characterized in including the determining step for determining the rotating velocity based on the TOC information read from the recording medium as the detecting step for detecting the rotating velocity of the recording medium and also determining the optimum read power corresponding to the rotating velocity detected in the detecting step and the radiating step for radiating, to the recording medium, the optical beam in which the write power is added to the optimum read power determined in the determining step.
According to another aspect of the present invention, the recording medium is characterized in consisting of the detecting step for detecting the rotating velocity of the recording medium, determining step for determining the optimum read power corresponding to the rotating velocity detected in the detecting step and the radiating step for radiating, to the recording medium, the optical beam in which the write power is added to the optimum read power determined in the determining step.
According to another aspect of the present invention, the recording medium is characterized in consisting of the determining step for determining the rotating velocity based on the TOC information read from the recording medium as the detecting step for detecting the rotating velocity of the recording medium and also determining the optimum read power corresponding to the rotating velocity detected in the detecting step and the radiating step for radiating, to the recording medium, the optical power in which the write power is added to the optimum read power determined in the determining step.
According to another aspect of the present invention, in the optical recording apparatus, optical recording method and recording medium, the rotating velocity of recording medium is detected, the optimum read power corresponding to the detected rotating velocity is determined and the optical beam of the power in which the write power is added to the determined optimum read power is radiated to the recording medium.